Companies need to recover capabilities and information quickly
when disasters strike. Failover requirements are stricter than ever
before. Linux-based clustering is growing in consideration and use
in telecommunications, banking and finance, e-commerce,
manufacturing, and other industry segments where high-availability
systems are needed. Linux cluster-software failover time is one of
the key variables of interest among the numerous products offered
to accommodate Linux-based clustering.

IP failover times provide a baseline for an actual
application-failover latency. (There are of course, many other test
points, features, and functions to consider.) Application-failover
times depend on the amount of state information to be restored, as
well as many other factors. If the IP failover time is, for
example, less than one second, then it may be fast enough to be
insignificant for many applications. However, if the application
failover itself must be less than one second, the lower the IP
failover latency, the more time remains to failover the application
itself within its constraints.

The report also details the requirements of the key blocks of a
proposed future hardware/software stack for such clusters. This
hardware stack includes such critical elements as application
management, cluster protocol, fault-management service, cluster
load-balancing service, message service, cluster event-notification
service, and virtual-interface architecture (VIA). All of the
stand-out products provide for remote administration - a critical
feature in many Linux deployments - and each offers cascading
failover, another vital capability. Data concerning significant
features and functions is provided for all these products and
dozens of other Linux cluster products.